Theoretical uncertainties in semileptonic B decay

The prospect of obtaining large data samples for B decays naturally raises the question of how precise predictions can be made for the detailed properties of these decays. Hence, this issue is relevant to a CP-violation oriented B-factory or to the high-luminosity option of the CERN LEP collider improvement program. In this paper, the authors address this issue in the context of the specific final state l bar v1 + X in B decay; that is, for the B decay of the semileptonic variety. Specifically, we consider various approaches to both exclusive and inclusive semileptonic B decay. The exclusive decay processes to u-like final states, which the authors define to be those exclusive states derived from b → u + l bar v1, when compared with the analogous exclusive decays to c-like final states, which the authors define to be those derived from b → c + l bar v1, allow the authors to determine, for example, the ratio |Vub|2/|Vcb|2, in principle, where VUD is the famous CKM mixing matrix. Hence, exclusive B decays may play an important role in the effort to determine the parameters of the standard SU2L x U1 model with high precision